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A checker function to use with learnr

Source: R/gradethis_exercise_checker.R
gradethis_exercise_checker.Rd

For exercise checking, learnr tutorials require a function that learnr can use in the background to run the code in each "-check" chunk and to format the results into a format that learnr can display. To enable exercise checking in your learnr tutorial, attach gradethis with library(gradethis), or call gradethis_setup() in the setup chunk of your tutorial. See gradethis_demo() to see an example learnr document that uses gradethis_exercise_checker().

Usage

gradethis_exercise_checker(
  label = NULL,
  solution_code = NULL,
  user_code = NULL,
  check_code = NULL,
  envir_result = NULL,
  evaluate_result = NULL,
  envir_prep = NULL,
  last_value = NULL,
  stage = NULL,
  ...,
  solution_eval_fn = NULL
)

Arguments

label

Label for exercise chunk

solution_code

Code provided within the "-solution" chunk for the exercise.

user_code

R code submitted by the user

check_code

Code provided within the "-check" (or "-code-check") chunk for the exercise.

envir_result

The R environment after the execution of the chunk.

evaluate_result

The return value from the evaluate::evaluate function.

envir_prep

A copy of the R environment before the execution of the chunk.

last_value

The last value from evaluating the user's exercise submission.

stage

The current stage of exercise checking.

...

Extra arguments supplied by learnr

solution_eval_fn

A function taking solution code and an envir (an environment equivalent to envir_prep) and that will return the value of the evaluated code. This callback function allows grading authors to write custom solution evaluation functions for non-R exercise engines. The result of the evaluated code should be an R object that will be accessible to the grading code in .solution or .solution_all.

You may also provide a named list of solution evaluation functions to the gradethis.exercise_checker.solution_eval_fn global option. The names of the list should match the exercise engine for which the function should be applied.

For example, for a hypothetical exercise engine echo that simply echoes the user's code, you could provide a solution_eval_fn that also just echoes the solution code:

options(
  gradethis.exercise_checker.solution_eval_fn = list(
    echo = function(code, envir) {
      code
    }
  )
)

Solution evaluation functions should determine if the solution code is missing and if so throw an error with class error_missing_solution (see rlang::abort() for help throwing this error).

Value

Returns a feedback object suitable for learnr tutorials with the results of the exercise grading code.

See also

gradethis_setup(), grade_this(), grade_this_code()

Examples

if (FALSE) {
gradethis_demo()
}